Pregnancy or just ovaluation cramps?

Me and my boyfriend had sex like 5 times about a week ago. We used condoms, however they kept slipping up whenever he pulled out at the end, so when his dick came out the condom and all the cum went all over the bed. After that I just washed my intimate areas just in case anything was around my vagina, although I didnt feel anything on it or inside. However, I’ve been having small cramps today and my lower back has been hurting, apart from that I didn’t have any other symptoms. I am also “apparently” at the middle stage of my fertility week which could also explain the cramps. However I’m just worried and do you guys think I could be pregnant? I’m pretty sure he didnt cum inside.

Im probably still going to take a pregnancy test just in case. Which one is the most effective and the quickest? And do I take them before my scheduled period or after? Or can I take them whenever I want?